High-frequency Rayleigh-wave tomography using traffic noise from Long Beach, California

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. B43-B53 ◽  
Author(s):  
Jason P. Chang ◽  
Sjoerd A. L. de Ridder ◽  
Biondo L. Biondi
Keyword(s):  
Traffic Noise ◽  
Long Beach ◽  
Low Velocity ◽  
Near Surface ◽  
Linear Feature ◽  
The North ◽  
Local Roads ◽  
Geologic Map ◽  
Wave Tomography ◽  
Dense Seismic Array

Using a dense seismic array in Long Beach, California, we have investigated the effectiveness of using traffic noise for passive subsurface imaging. Spectral analysis revealed that traffic-induced vibrations dominate the ambient seismic noise field at frequencies between 3 and 15 Hz. Using the ambient-noise crosscorrelation technique at these frequencies, we have extracted fundamental- and first-order-mode Rayleigh waves generated by Interstate 405 and local roads. We picked group traveltimes associated with the fundamental mode and used them in a straight-ray tomography procedure to produce group velocity maps at 3.0 and 3.5 Hz. The velocity trends in our results corresponded to shallow depths and coincided well with lithologies outlined in a geologic map of the survey area. The most prominent features resolved in our velocity maps were the low velocities to the north corresponding to less-consolidated materials, high velocities to the south corresponding to more-consolidated materials, a low-velocity zone corresponding to artificial fill in Alamitos Bay, and a low-velocity linear feature in the Newport-Inglewood Fault Zone. Our resulting near-surface velocities can be useful for identifying regions that are susceptible to serious damage during earthquake-related shaking.

Seismic mapping of on-shore sediments at Andøya, Norway, deposited prior to the North Atlantic rifting

2020 ◽  
Vol 8 (4) ◽  
pp. SQ105-SQ114
Author(s):  
Tor Arne Johansen ◽  
Bent Ole Ruud ◽  
Tormod Henningsen ◽  
Marco Brönner
Keyword(s):  
North Atlantic ◽  
Seismic Velocity ◽  
Traffic Noise ◽  
Seismic Exploration ◽  
Small Scale ◽  
Near Surface ◽  
The North ◽  
Seismic Surveying ◽  
The North Atlantic ◽  
Seismic Velocity Contrasts

Andøya is an island in the north of Norway. On its eastern side, it contains a local downfaulted basin of Mesozoic sediments sheltered from erosion during subsequent periods of Pleistocene glaciation. The sediments were deposited before the North Atlantic rifting and partly overlie weathered basement. We have recently carried out seismic surveying to better understand the geometry and seismic responses of the basin system. Extensive civil infrastructure and wet mire made the study area challenging for seismic exploration. We shot the survey lines at wet mire with detonating cord during winter when the mire was frozen. In the summer, we conducted seismic surveying along road shoulders with a small-scale vibrator. The seismic processing was particularly challenging due to the influence of traffic noise, heterogeneous near-surface conditions, and large seismic velocity contrasts. We interpreted the seismic lines in integration with other geophysical data and well logs to obtain a consistent and best possible seismic model of the basin. Our interpretation indicates a reorganization of the regional paleostress regime that took place during the continental breakup in the Eocene. In spite of severe obstacles for seismic surveying of the area, our results honor the robustness of the seismic method for subsurface imaging.

Evaluation of the relation between near-surface geological units and ground response in the vicinity of Long Beach, California

1979 ◽  
Vol 69 (5) ◽  
pp. 1603-1622
Author(s):  
A. M. Rogers ◽  
J. C. Tinsley ◽  
W. W. Hays ◽  
K. W. King
Keyword(s):  
Strong Motion ◽  
Test Site ◽  
Peak Ground Velocity ◽  
Long Beach ◽  
Spectral Ratios ◽  
Low Velocity ◽  
Ground Response ◽  
Near Surface ◽  
Long Period ◽  
Short Period

abstract Simulataneous recordings of Nevada Test Site nuclear events were made at sites underlain by alluvium in the Long Beach, California, area and at sites underlain by rock in the Palos Verdes and Pasadena areas. These data show peak-ground-velocity alluvium-to-rock ratios as large as 7 and spectral ratios as high as 11 in the period band from 0.2 to 6 sec. Comparison of the low-strain nuclear-explosion data and the San Fernando earthquake strong-motion data at three sites indicates that the alluvium-to-rock spectral ratios derived from the nuclear explosions are similar to those derived from the earthquake. Significant trends exist in the short-period data, indicating higher ground response at sites underlain at the near-surface by materials that have high void ratios and lower ground response with increasing thickness of Quaternary deposits. These results suggest that the short-period response is primarily controlled both by near-surface low-velocity layers and by attenuation in the Quaternary sediments. Comparison of the data of this study with data collected in other areas indicates that the long-period response increase with either increasing depth to basement or with alluvium thickness, when this thickness is greater than 400 m. From previous theoretical studies and these results, ground response in the long-period band is related to those underlying geological structures and major velocity contrasts that control the development of surface waves.

scholarly journals Near surface structure of the North Anatolian Fault Zone from Rayleigh and Love wave tomography using ambient seismic noise

2018 ◽  
Author(s):  
George Taylor ◽  
Sebastian Rost ◽  
Gregory Houseman ◽  
Gregor Hillers
Keyword(s):  
Phase Velocity ◽  
Fault Zone ◽  
North Anatolian Fault ◽  
Fault System ◽  
Velocity Variation ◽  
S Wave ◽  
North Anatolian Fault Zone ◽  
Near Surface ◽  
The North ◽  
Wave Tomography

Abstract. We use observations of surface waves in the ambient noise field recorded at a dense seismic array to image the North Anatolian Fault Zone (NAFZ) in the region of the 1999 magnitude 7.6 Izmit earthquake in western Turkey. The NAFZ is a major strike slip fault system extending ~ 1200 km across northern Turkey and poses a high level of seismic hazard, particularly to the city of Istanbul. Assuming isotropy, we obtain maps of phase velocity variation using surface wave tomography applied to Rayleigh and Love waves and construct high resolution images of S-wave velocity in the upper 10 km of a 70 km by 30 km region around Lake Sapanca. We observe low S-wave velocities (< 2.5 km s−1) associated with the Adapazari and Pamukova sedimentary basins, as well as the northern branch of the NAFZ. In the Armutlu Block, between the two major branches of the NAFZ, we detect higher velocities (> 3.2 km s−1) associated with a shallow crystalline basement. We measure azimuthal anisotropy in our phase velocity observations, with the fast direction seeming to align with the direction of maximum extension for the region (~ 45°). The signatures of both the northern and southern branches of the NAFZ are clearly associated with strong gradients in seismic velocity that also denote the boundaries of major tectonic units. Our results suggest that the development of the NAFZ has exploited this pre-existing contrast in physical properties.

High-frequency Rayleigh-wave tomography using traffic noise from Long Beach, California

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. B1-B11 ◽  
Author(s):  
Jason P. Chang ◽  
Sjoerd A. L. de Ridder ◽  
Biondo L. Biondi
Keyword(s):  
Rayleigh Wave ◽  
High Frequency ◽  
Traffic Noise ◽  
Long Beach ◽  
Wave Tomography ◽  
Rayleigh Wave Tomography

scholarly journals Evidence of stretching of the lithosphere under Denmark

2008 ◽  
Vol 15 ◽  
pp. 53-56
Author(s):  
Søren Gregersen ◽  
Lene Vandur Nielsen ◽  
Peter Voss
Keyword(s):  
Field Work ◽  
P Wave ◽  
Depth Interval ◽  
Low Velocity ◽  
Teleseismic Tomography ◽  
The North ◽  
Crystalline Crust ◽  
Wave Tomography ◽  
National Boundaries ◽  
The Many

The structure of the lithosphere under Denmark has been investigated in relation to adjacent regions of Sweden and Germany. The most interesting result of the study is that the 120 km thick lithosphere under Denmark appears to be a stretched version of the Swedish lithosphere, which is more than twice as thick. During the international project Tele seismic Tomography across the Tornquist Zone (Tor), field work and international interpretation were carried out between 1996 and 2002. Following the field work period, modelvelocity computations were undertaken based on ob ser vations of distant earthquakes (e.g. Arlitt 1999; Shomali et al. 2002; Voss et al. 2006), and recently an evaluation of the Tor results was completed (Nielsen 2007). The Tor project investigates deeper parts of the Earth than previous projects, and in particular the depth interval 50–300 km, which is below the crystalline crust. The investigations have included many geophysical features such as teleseismic P-wave tomography, Rayleigh wave velocities, shear wave splitting and wave scattering. We have distinguished between relatively high- and low-velocity zones, which also show variations in anisotropy and scatter characteristics. Generalised high-velocity zones correspond to the lithosphere, while generalised relatively low-velocity zones are equivalent to the asthenosphere. The main outcome of the combined studies is that the deep lithosphere can be divided into three blocks separated approximately along the national boundaries between Sweden and Denmark and between Denmark and Germany. The boundaries between the blocks are steep, almost vertical. The Denmark block has lithosphere properties between those to the north and south. Based on previous crustal studies and the Tor results, we suggest that the Denmark block has evolved by stretching. The details in the new evaluation are derived from teleseismic tomography. Here we present a synthesis of the many derived models in the light of the new evaluation.

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